Silver Recovery from Jarosite Residue Using NADES (Reline)–Water Mixtures: Characterization and Leaching Performance

Jarosite residues generated during zinc hydrometallurgy may retain valuable metals such as silver within complex and poorly accessible mineral phases. In this study, hydrated reline, a choline chloride–urea natural deep eutectic solvent (NADES), was evaluated as an alternative leaching medium for silver recovery from an industrial jarosite residue. Reline/water mixtures containing 10, 20, and 30 wt.% water (RE9010, RE8020, and RE7030, respectively) were investigated to determine the influence of solvent hydration and temperature (25–80 °C) on silver extraction. Mineralogical characterization by XRD, SEM–EDS, and automated TIMA analysis revealed a heterogeneous residue in which silver-bearing phases are associated with complex mineral assemblages, potentially limiting their accessibility during leaching. Among the evaluated systems, RE9010 consistently exhibited the highest silver recovery, increasing from 12.83% at 25 °C to 24.10% at 80 °C. Successive leaching cycles further increased the cumulative silver recovery to 34.7% for RE9010. FTIR analysis showed that the characteristic spectral features of reline were preserved after the addition of up to 30 wt.% water. Kinetic analysis indicated that diffusion-based models provided the best description of the leaching behavior, with the Zhuravlev–Lesokhin–Templeman model showing the best overall fit. An apparent activation energy of 18.4 kJ mol−1 was obtained, supporting the contribution of mass-transfer and diffusion phenomena to the overall process. These results demonstrate that controlled hydration and moderate heating can improve the leaching performance of reline while preserving its characteristic interactions, highlighting its potential as an alternative solvent for silver recovery from complex metallurgical residues.